Polyaminomethylenephos phonate derivatives

ABSTRACT

A new class of polyaminophosphonate derivatives usable as inhibitors of precipitation and dispersants in aqueous systems. The products in object have complete tolerance of calcium and can be employed in severe conditions of use in the water treatment and detergent fields.

The present invention relates to a new class of phosphonates and relatedsalts, the method of preparation of the same and their utilization inthe preparation of water additives to be used in different industrialfields. More particularly, the present invention relates to thepreparation of products that impart to the water the particularcharacteristics needed for its utilisation. More specifically, theproducts and the processes according to the present invention makeavailable new additives that prevent the segregation of solids fromtheir aqueous solutions or dispersions acting as precipitationinhibitors and dispersants.

The present invention will be here described with particular referenceto the preparation and to the use of the products and processes for thepreparation and the stabilization of aqueous dispersions, even thoughits scope should not be limited to those possible applications of theinvention described above.

It is known that water found in the natural state (apart from rainwater)in the form of rivers, lakes and seas contains a certain quantity ofmetal ions and anions of different types in various proportions,depending on their origins; such metal ions can lead to the formation ofa precipitate when water taken from a natural environment is used forindustrial purposes. In this conditions, water which is normally inequilibrium with the external environment is affected by differentphysical-chemical conditions and if the concentration of salts in thesenew conditions exceeds the solubility product (supersaturation) theirprecipitation is observed during the utilisation.

Salts showing this phenomenon are generally formed by earth-alkalimetals (Ca; Ba; Mg); among them Calcium—mostly as carbonate but also assulfate—is the main responsible for the phenomena of incrustation inseveral industrial water applications.

The incrustation (not only limited to poory soluble salts) is generallycalled “SCALE” by water treatment experts.

Several factors are responsible for “supersaturation” and thus for theprecipitation of aqueous solutions containing calcium carbonate. TheCaCO₃/CO₂/H₂O system is described schematically here:

Calcium is present in all surface waters in the form of solublebicarbonate (HCO₃ ⁻) because of the absorption of carbon dioxide fromthe atmosphere. Any modification of such a system leads, in a more orless marked way, to precipitation of the CaCO₃.

The causes are different and can be classified as follows:

-   1. Concentration of the solution (evaporation of the aqueous phase);-   2. Variation of the temperature. By heating, the following    transformation Ca(HCO₃)₂ CaCO₃+CO₂+H₂O takes place.-   3. Variations of the pH. An increase of the pH of the system results    in the following transformation:-   4. Ca(HCO₃)₂+2OH⁻→CacO₃+CO₃ ⁻+2H₂O

As far as cooling and/or heat-exchanger circuits is concerned, theincrustation (scale) formation mechanism can be attributed toprecipitation of salts from supersaturated solutions in the regionadjacent to the heat exchange surface of the system.

The effects of such uncontrolled precipitation are sometimes disastrous.For example, in cooling systems, where large volumes of water are used,the deposits of CaCO₃ accumulate in big quantity in the pipes causingreduction of the thermal exchange capacity and leading to virtualocclusion of the pipes making necessary the removal of the deposits byacidic treatment with consequent shutdown of the plant Moreover, theformation of CaCO₃ incrustation facilitates the incorporation of solidparticles that cannot be chemically removed (e.g. SiO₂) or the growth ofbacteria and algae.

In order to overcome these disadvantages, pretreatments have beenproposed: they provide for the preventive elimination of low-solubilitysalts by ionic exchange, precipitation, or by the use of suitable“sequestering agents” and suitable “scale inhibitors”. Preventiveelimination is in most cases not economically acceptable because of thelarge volumes of water involved.

The same can be said for the chelating agents; it is well known thatthese substances forms water-soluble complexes with the metal ions, in awell defined stoichiometric molar ratio. The preferred treatment todayinvolves for the use of suitable “scale inhibitors” using the so called“Threshold Effect”. The Threshold Effect was discovered by observing thebehaviour of inorganic polyphosphates that prevent the precipitation ofthe CaCO₃ from supersaturated solutions by means of sub-stoichiometricconcentrations (Hatch and Rice, Indust. End. Chem. 31, 51-53 (1939);Reitemeier and Buehrer, J. Phys. Chem. 44 (5), 535-536 (1940); Fink andRichardson U.S. Pat. No. 2,358,222; and Hatch, U.S. Pat. No. 2,539,305).

The mechanism by which the precipitation is inhibited is not completelyunderstood today, although the adsorption of inhibitor onto thecrystalline surface seems necessarily to be the first step in theinhibition process. The molecules of inhibitor are attracted on thegrowing crystalline surface by the presence of metal cations such as Ca,Mg, Ba for which they have a great affinity.

Once the molecules of inhibitor are adsorbed, they locate on the surfaceof the crystal, thus disturbing the regularity of its growth.

If all this happens in the “nucleation” phase, i.e. in the stage inwhich a certain number of molecules in solution begin to aggregate inorder to give rise to a crystal nucleus, the inhibitor can disturbnuclear growth to such an extent as to make the nucleus redissolve.

Such ability, exercised by various polyelectrolytes, is particularlymarked in the case of phosphonates, which moreover combine corrosioninhibition functions with great resistance to hydrolysis.

However, for every operating condition there is a limit to the molarratio between inhibitor and metal. In fact, by increasing thephosphonate quantity beyond a certain limit, precipitation of insolublecalcium salts of phosphonates is observed; in such “turbidity” zone, thephosphonate is no longer active. The effectiveness of the phosphonatesat various inhibitor/metal ratios is shown schematically in FIG. 1,where the x-axis reports the molar ratio between metal and inhibitor,while the y-axis reports the turbidity measured nephelemetrically.

Furthermore, it is well known that it is necessary to provide for morecritical recovery cycles of industrial water—above all because of anincreasing use of water resources—in order to reduce both the quantityof water used and the environmental impact of the treatment agents.

SUMMARY OF THE INVENTION

The present invention relates to a new class of phosphonates, to asimple and economic process for the production of said new class ofphosphonates and to the use of said phosphonates in water treatmentapplications. Therefore, the main object of the present invention is anew class of phosphonates that can be used for water treatment.

The compounds that form the object of the present invention are thederivatives of polyaminomethylenephosphonates having the followinggeneral formula:

where n is an integer between 2 and 15000 preferably between 2 and 50;M₂ may be hydrogen or a suitable cation and each R group may be a—CH₂—PO₃M₂, group or a linear or branched alkyl residue resulting fromthe reaction of the groups with the following reagent classes:1)

where R¹ may be H, CH₃, CH₂Cl, CH₂OH2)

where R₂ is an alkyl with the number of carbon atoms between 3 and 5.3)

where Z is a group from among: CONH₂, CHO, COOR₃ COOX, CN, where R₃═CH₃,C₂H₅, and where X═H, Na, K, NH₄.

In Particular, the compounds that form the object of the presentinvention are the derivatives of polyaminomethylenephosphonatesaccording to the above mentioned formula where the polyamine chain maybe linear or branched, and where n is an integer or fractional integerwhich is, or on average is, from about 2 to about 15000: M₂ may behydrogen or a suitable cation such as alkali metal or ammonium, andwhere each R group my be the same or different and is independentlyselected from the following classes:

-   1. —CH₂PO₃M₂    -   where M may be hydrogen or a suitable cation such as alkali        metal or ammonium;-   2. CH₂R    -   where R=CH₂OH; CHOHCH₃; CHOHCH₂Cl; CHOHCH₂OH-   3. (CH₂)_(n)SO₃M    -   where n=3÷4 where M may be hydrogen or a suitable cation such as        alkali metal or ammonium;-   4. CH₂CH₂R    -   where R=CONH₂, CHO, COOR₁, COOX, CN    -   where R₁=CH₃+C₂H₅    -   where X may be hydrogen or a suitable cation such as alkali        metal or ammonium with the condition that at least one of        substituent R should be different from the methylenephosphonated        group (i.e.: other than —CH₂PO₃M₂).

A particular advantage of this new class of phosphonates, object of thisinvention, is that such compounds do not show “Turbidity Zone” and aretherefore to be considered non Calcium-sensitive at any concentrationand temperature tested; they are also effectives at high pH values(>10).

This is very important since calcium tolerance of the traditional scaleinhibitors like HEDP or ATMP quickly reduces with increasing the pH; inparticular this is important today because water treatment processes arecarried out at higher pH values than in the past. In fact, higher pHreduces the effects of corrosion, which is more marked at lower pH.

The advantages of this new class of phosphonates, object of thisinvention, that can be summarised as follows:

-   1. Threshold Effect, typical of the phosphonates, i.e. inhibition of    precipitation from solutions supersaturated with CaCO₃ and/or CaSO₄    at sub-stoichiometric concentrations of the inhibitor.-   2. Non calcium-sensitivity: increases in pH and concentration of    calcium strongly affect the tolerance of the standard phosphonates    (HEDP, ATMP, etc.) to calcium, increasing the possibility of    precipitation of poorly soluble calcium-phosphonate salts.-   3. Dispersing Effect: better than the traditional phosphonates. This    new class of phosphonates behaves like the acrylic polymers. They    act as dispersants and deflocculants, stabilizing colloidal systems    which remain steadily dispersed for long periods.-   4. Corrosion Inhibition: comparable to that of the standard    phosphonates.-   5. Chelating Effect: comparable to that of the standard    phosphonates.-   6. Hydrolitic Stability: similar to conventional phosphonates

As shown in point 3) above, in addition to the threshold effect, theproducts object of the present invention shows high “dispersingability”.

This property became evident when the sequestering power is determinedby the traditional “HAMPSHIRE” method: with this method it is notpossible to identify an end-point during the titration with calciumacetate. This property suggests a potential application of this newclass of phosphonates as deflocculants, in a certain number of processesand applications where they are involved as stabilizers for differentkind of dispersions like pigments (TiO2), kaolin and drilling mudstabilizers for different rind of dispersions like pigment (TiO2),kaolin and drilling mud and in the industrial and domestic detergentfield for their ability to disperse dirt particles. From a general pointof view, thanks to their particular properties the products according tothe present invention can be used for;

-   -   reverse osmosis system;    -   scale removal;    -   scale prevention and corrosion control;    -   boiler cleaning;    -   bottle washing;    -   hard surface cleaners;    -   cooling system;    -   slurry dispersion;    -   textile processing;    -   sanitary cleaners;    -   paints;    -   secodnary oil recovery;    -   oil drilling muds;    -   laundry detergents;    -   industrial cleaners;    -   peroxide stabilisation;    -   metal finishing;    -   meta cleaners;    -   geothermal water;    -   set retardens for concrete    -   car wash;    -   flash desalination.

Obyect of the present invention is also a simple and economic processfor the preparation of the phosphonates and their utilisation in theabovesaid fields, particularly as inhibitors of the formation,deposition, and adhesion of incrustations caused by insoluble salts ofalkali-earth metals, in particular Ca⁺⁺, Mg⁺⁺, on metal surfaces ofaqueous systems (cooling towers, boilers, gas scrubbers etc.)

The compounds object of this invention is prepared byphosphonomethylation reaction of polyamine or mixtures of polyamines, bymeans of the Mannich reaction illustrated hereunder.

The phosphonomethylation reaction of amines according to Mannich isdescribed in the literature, eg: K. Moedritzer and R. Irani, J. Organic.Chem. 31 (5) 1603-7: any relevant reference is to be consideredmentioned herein to fully complete the invention specifications.

A typical procedure provides for the amine to be slowly added to amixture of phosphorous acid and hydrochloric acid. The reaction mixturethus obtained is heated to reflux with addition of formaldehyde. Thereaction time can vary from 1 to 5 h.

The derivatives of the polyaminomethylenephosphonate object of thisinvention are added to the aqueous systems in quantities between 2 and50 mg/l in order to inhibit precipitation, deposition and adhesion ofscale, especially CaCO₃.

The expression “inhibits precipitation and formation of deposits”includes threshold effect, dispersion, solubilization or modification ofthe precipitate's morphology. The expression “inhibits the adhesion”defines just that scale is easily removed e.g. by simple washing/rinsingand not by mechanical or chemical treatment, not being the incrustationstrongly bonded to the surface to which it adheres.

The term “scale” includes incrustation formed by CaCO₃, CaSO₄, BaSO₄deposit and can be extended in a generalized manner to alllow-solubility salts of several cations (Mg, Fe, ectc.). The term“aqueous systems” refers to industrial and/or commercial systems thatuse water in heat-exchange processes and includes cooling towers,boilers, desalination systems, gas scrubbers; furthermore, processes ofdesalination by Reverse Osmosis (RO) are included. Of particularimportance are systems operating in severe conditions such as high pHand high concentrations of calcite (CaCO₃). The preparation and theapplication of the polyaminomethylenephosphonate derivatives object ofthe present invention are illustrated in the following examples, whichclarify their applications, without however limiting the scope.

EXAMPLE 1

Into a suitable reaction vessel 350-g of triethylenetetramine werecharged; thereafter the reaction mixutre was heated at 90÷95° C.

Ethylene oxide was than added stepwise at such a rate that, withexternal cooling applied, the temperature did not exceed 100° C.

211 g of ethylene oxide had been added over a period 1½ hours. Theresultant product was then converted in the phosphonomethylatedderivates according to Mannich's reaction.

With the same synthetic path is possible to obtain β hydroxyethylderivates of linear or branched polyamines or mixture of them in a rightratio. Other compounds of these invention can be prepared according tothe procedure above describe using propylene oxide instead of ethyleneoxide (β hydroxy propyl derivates).

EXAMPLE 2

Into a suitable reaction vessel 292 g of triethylenetetramine werecharged.

Under stirring acrylonitrile was than added stepwise at such a ratethat, with external cooling applied, the temperature did not exceed 50°C.

212 g of acrylonitrile had been added over a period 2 hours. Theresultant product was than converted in the phosphonomethylatedderivates according to Mannich's reaction.

With the same synthetic path is possible to obtain β cyanoethylderivates of linear or branched polyamines or mixture of them in a rightratio.

EXAMPLE 3

Into a suitable reaction vessel 292 g of triethylenetetramine werecharged

Under stirring 488 g of 1,3-propane sultone, dissolved in 1140 g ofmethanol, was added dropwise at a tempearture between 40°÷50° C. After 2hours, the methanol was removed by evaporation to dryness and theresidue dissolved in water. The resultant product was than converted inthe phosphonomethylated derivates according to Mannich's reaction.

With the same synthetic path is possible to obtain N-(sulfopropane)amino derivates of linear or branched polyamines or mixutre ofthem in a right ratio.

Other compounds of these invention can be prepared according to theprocedure above describe using epichlorohydrin or other differentoxiranes derivates instead of 1,3 propane sultone.

EXAMPLE 4

Into a suitable reaction vessel 234 g of compound of example 1 wereadded to a 70% phosphorous acid solution (478 g) and 32% of hydrochloricacid (342 g). The mixture thus obtained was heated to reflux, 340 g of37% aqueous formaldehyde solution was added phosphorous acid solution(478 g) and 32% of hydrochloric acid (342 g). The mixture thus obtainedwas heated to reflux, 340 g of 37%, aqueous formaldehyde solution wasadded dropwise in the course of ca 1 hr and the reaction mixture waskept at reflux temperature for 1 additional hr. 300 g volatilessubstances was then removed from the reaction mixture by distillation.The final product obtained was a viscous fluid having an activesubstance of 50%. Infrated analysis of the product showed the presenceof methylenephosphonic amine groups, while P³¹ NMR analysis indicatethat at least 90% of the amine groups had been phosphonomethylated. Theimpurities include unreacted phosphorous acid, phosphoric acid and otherunidentified compounds.

By following the same synthetic method it is possible to obtainpbosphonometilated derivates of polyamine or mix of polyamine havinggroup selected from the following class:

-   1. C₂O₃M₂    -   where M may be hydrogen or an suitable cation such as alkali        metal or ammonium;-   2. CH₂R    -   where R=CH₂OH; CHOHCH, CHOHCH₂Cl; CHOHCH₂OH-   3. (CH₂)_(n)SO₃M    -   where n=3÷4 where M may be hydrogen or a suitable cation such as        alkali metal or ammonium;-   4. CH₂CH₂R    -   where WR=CON₂, CHO, COOR₁COOX, CN    -   where R₁=CH₃÷C₂H₅    -   where X may be hydrogen or a suitable cation such as alkali        metal or ammonium.

Where preferably at least one or more than one substituent R isdifferent from the methylenephosphonated group.

EXAMPLE 5 Threshold Effect on CaCO₃ at p=10, T=70° C. 100 ppm of CaCO₃

The method describes the procedure for the determination of theThreshold Effect, that is the ability of a dispersing agent, present insubstoichiometric amounts, to inhibit the precipitation of solutionssupersaturated with calcium carbonate in deionized water.

This method measures the efficiency of a dispersant by titration of theCalcium ion remaining in a solution supersaturated with CaCO₃respectively before and after treatment in a oven at 70° C. The greaterthe calcium concentration after the period in the oven, the greater theefficiency of the dispersant in preventing precipitation of CaCO₃.

Increasing substoichiometric amounts of phosphonate are dissolved insolutions containing [Ca⁺⁺] and [CO₃ ⁻] obtained by mixing proper CaCl₂and Na₂CO₃ solutions.

The precipitation of calcium carbonate is measured by titration of thefiltered solution. The results obtained are summarised in table 1. TABLE1 Operating Conditions: 100 ppm CaCO₃; pH = 10; T = 70° C.; 24 hInhibition % Inhibitor 0.25 ppm 0.5 ppm 1 ppm Example 4 72 97 99 HEDP 7499 100 ATMP 75 99 100 DTPMP 65 85 100 PBTC 90 100 100HEDP = Hydroxy-ethylydene-1,1-diphosphonic AcidATMP = Amino-tris Methylenephosphonic AcidDTPMP = Diethylenetriamine penta (methylenephosphonic acid)PBTC = Phosphono Butane tris Carboxylic Acid

Following the method described in example 5, the following results wereobtained: TABLE 2 Operating Conditions: 400 ppm CaCO₃; pH = 11.5; T =40° C.; 24 h Inhibition % Inhibitor 40 ppm 80 ppm 200 ppm 400 ppm 450ppm Example 4 0 35 90 92 95 ATMP 0 35 40 60 65 DTPMP 0 35 83 80 80 PBTC0 30 42 92 95

EXAMPLE 6 CaSO₄ Threshold Effect at pH=7; T=70° C.: 6800 ppm of CaSO₄

Following the method described in example 5. In the specific case thesolution of CaSO₄ was prepared starting from CaCl₂ and Na₂SO₄. Theresults obtained are hereunder summarised: TABLE 3 Operating Conditions:6800 ppm CaSO₄; pH = 7; T = 70° C.; 24 h Inhibition % Inhibitor 0.5 ppm1 ppm 2 ppm 5 ppm 10 ppm Example 4 10 10 90 100 100 DTPMP 10 22 75 95100

EXAMPLE 7 CaSO₄ Threshold Effect at pH=7: T=70° C.: 6800 ppm ofCaSO₄+6000 ppm of Ca⁺⁺

Following the method described in example 4. In the specific case thesolution of CaSO₄ was prepared starting from CaCl₂ and Na₂SO₄.

The results obtained are summarised in table 4. TABLE 4 OperatingConditions: 6800 ppm CaSO₄ + 6000 ppm di Ca⁺⁺; pH = 7; T = 70° C.; 24 hInhibition % Inhibitor 2 ppm 5 ppm 10 ppm Example 4 15 91 99 DTPMP 22 4596

EXAMPLE 8 CaSO₄ Threshold Effect at pH=7; T=90° C.: 6890 ppm of CaSO₄

Following the method described in example 5. In the specific case, thesolution of CaSO₄ was prepared starting from CaCl₂ and Na₂SO₄. Theresults obtained are summarised in table 5. TABLE 5 OperatingConditions: 6800 ppm CaSO₄; pH = 7; T = 90° C.; 24 h Inhibition %Inhibitor 0.5 ppm 1 ppm 2 ppm 5 ppm 10 ppm Example 4 0 5 18 85 99 DTPMP0 0 5 73 90

EXAMPLE 9 CaSO₄ Threshold Effect at pH=7; T=90° C.: 6800 ppm ofCaSO₄+6000 ppm of Ca⁺⁺

Following the method described in example 5. In the specific case, thesolution of CaSO4 was prepared starting from CaCl₂ and Na₂SO₄. Theresults obtained are summarised in table 6. TABLE 6 OperatingConditions: 6800 ppm CaSO₄ + 6000 ppm di Ca⁺⁺; pH = 7; T = 90° C.; 24 hInhibition % Inhibitor 0.5 ppm 1 ppm 2 ppm 5 ppm 10 ppm Example 4 10 1518 91 99 DTPMP 0 0 8 38 45

Calcium-Sensitivity EXAMPLE 10

The Grace “CLOUD POINT TEST” was used for testing thecalcium-sensitivity. This simple method allows calcium-sensitivity to beverified visually by estimating the turbidity point of an inhibitorsolution in a concentrated calcium solution. The inhibitor is added atincreasing amounts to hard water having the following characteristics:500 ppm of Ca++(as CaCl₂), pH=8.3 (0.05 M of Boric buffer), at atemperature of 60° C. and 100° C. for 24 h.

The turbidity of solutions after 24 hours was observed. The observationconfirmis that the turbidity is greater at increasing amounts ofinhibitor. The results obtained are summarised in table 7 and 8. TABLE 7500 ppm CaCO₃; pH = 8.3; T = 60° C. Inhibitor Dose Inhibitor 10 ppm 30ppm 50 ppm 100 ppm Example 4 clear clear clear clear ATMP clear turbidprecipitate precipitate

TABLE 8 500 ppm CaCO₃; pH = 8.3; T = 100° C. Inhibitor Dose Inhibitor 10ppm 30 ppm 50 ppm 100 ppm Example 4 clear clear clear clear AMTPprecipitate precipitate precipitate precipitate

Fe³⁺ Sequestering EXAMPLE 11

The measurement of the sequestering power of iron is difficult both fortraditional phosphonates and for polyaminomethylenephosphonatederivatives, object of this invention: both products have considerabledispersing ability and if we considerer the colloidal aspect of theferric hydrate it is clear how difficult it could be to distinguishbetween the dispersed iron and the iron effectively sequestered; it iswell known that a very fine dispersion is very similar to a solution. Itmust be said that often in practical applications an effectivedispersion as useful as a true sequestration.

The method consists in the addition a known quantity of solution offerric ions to an aqueous solution of inhibitor at constant pH. After 24hours under agitation the aspect of the sample is evaluated. The sampleswhere a precipitate is present after 24 hours of agitation areconsidered “precipitated” and so the first clear sample has beenconsidered in order to attribute a sequestring value. The resultsobtained are summarsed in table 9. TABLE 9 Fe3+ Sequestering Powerexpressed as mg Fe3+/g of product Inhibitor pH = 5 pH = 6 pH = 7 pH = 8pH = 9 pH = 10 pH = 11 pH = 12 Example 4 0 60 180 200 260 360 200 20HEDP 240 280 320 360 800 800 1200 1200 ATMP 40 60 100 120 140 180 120 0DTPMP 40 60 80 140 220 130 60 20

These data should be carefully evaluated because the method utiliseddoes not allow dispersion to be distinguished from true chelation;however, internal comparison indicate that traditional phosphonates andthe derivatives object of the present invention are equally effective inthe control of ferric ion.

Corrosion Inhibition

The corrosion of metal equipment is an almost universal problem foraqueous systems: on a metal surface two distinct areas coexist, anodeand cathode, which in practice may be situated very close to each otherand set up an electrical circuit with consequent Redox reactions leadingto the solubilization of the metals. In particular iron surfaces aretransformed into water-soluble Fe^(2+/3+) ions. The corrosion, andtherefore the loss of metal from part of the structure, takes place onlyin the anodic zone.

Without entering into the detail of the corrosion phenomenon, it isclear, however, that the damage caused by corrosive phenomena can beconsiderable in extent. Various methodologies and various products havebeen developed in the time to solve the problems related to the entityand various origins of the corrosive phenomena. One of the morewidespread methodologies involves the use, in aqueous phase, of suitable“corrosion inhibitors”. These compounds which can be organic orinorganic films or protective barriers between the metal surface and theof corrosion medium. This protective film formed can be:

-   1.1. Precipitation of inhibitor onto the metal surface-   2.2. Passivation of the metal surface-   3.3. Adsorption of inhibitor onto the metal surface through the    electronic lone pair of some donor elements (N, S, O, P).

EXAMPLE 12

In the following example a simple test is described for the evaluationof the efficiency of the compounds object of this invention as corrosioninhibitors. The operating conditions and the procedure used in the testare indicated below:

Take a water with 30 French degrees of hardness, brought it at pH=8.5with diluted NaOH and than add the desired quantity of inhibitor.

Add carefully cleaned and weighed steel coupons to the solution

The test lasts 5 days with a constant airflow bubbled through thesolution.

After 5 days, weigh the test pieces and the loss in weight is estimate.

The results obtained are summarised in the following table: TABLE 10Inhibitor % weight loss after 5 days Example 4 0.25 ATMP 0.45 HEDP 0.3Blank 0.7

1) Polyaminomethylenephosphonate derivatives, useful to carry out watertreatments, of general formula

where n is between 2 and 15000; M₂ can be hydrogen or a suitable cationand each R group can be a —CH₂PO₃M₂ group, or linear or branched alkylresidue resulting from the reaction of the terminal amine groups withthe following reagent classes:
 1.

where R₁ can be H, CH₃, CH₂Cl, CH₂OH.
 2.

where R₂ is an alkyl with a carbon atom number between 3 and 5,
 3.

where Z is a group chosen from: CONH₂, CHO, COOR, COOX, where R═CH₃,C₂H₅, and where X═H, Na, K, NH₄. 2) Polyaminomethylenephosphonatederivatives according to the preceding claim wherein n is preferablybetween 2 and 15000, and each R group, being the same or different, isindependently selected from the following classes:
 1. CH₂PO₃M₂ where Mmay be hydrogen or an suitable cation such as alkali metal or ammonium;2. CH₂R con R=CH₂OH; CHOHCH₃; CHOHCH₂Cl; CHOHCH₂OH
 3. (CH₂)_(n)SO₃M conn=3÷4 where M may be hydrogen or a suitable cation such as alkali metalor ammonium;
 4. CH₂CH₂R con R=CONH₂, CHO, COOR₁, COOX, CN conR₁=CH₃÷C₂H₅ where X may be hydrogen or a suitable cation such as alkalimetal or ammonium. With the premise that at least one of substituent Ralways is different from CH₂PO₃M_(z). 3) Polyaminomethylenephosphonatederivatives according to claim 2 wherein also at least on of theterminal CH₂PO₃H₂ mojeties are substitued by one of the mojeties underthe above points 1 to
 4. 4) Process for the preparation of thepolyaminomethylenephosphonate derivative according to claims 1 or 2,comprising phosphonomethylation of polyamine derivatives by means ofMannich reaction. 5) Use of polyaminomethylenephosphonate derivativeaccording to claim 2 as scale inhibitors. 6) Use ofpolyaminomethylenephosphonate derivative according to claim 2 assequestring agents. 7) Use of polyaminomethylenephosphonate derivativeaccording to claim 2 as corrosion inhibitors.